The referenced patent application Ser. No. 214,481, filed Dec. 9, 1980, MULLER et al, describes a sensor arrangement in which oscillations which occur upon knocking or premature combustion of the fuel-air mixture within the cylinder of an internal combustion engine are sensed. An optical receiver, for example a photo diode, photo transistor, photo resistor, or the like, is optically coupled to the combustion chamber. Coupling can be effected by a glass rod, for example passed through an electrode of a spark plug, or by embedding light guide fibers or light guide fiber cables in a suitable location in the combustion chamber, so that the light guide fibers or cables will pick up light generated upon combustion. In accordance with the disclosure of this application, the light guide fibers or cables can be placed within the cylinder head gasket, and suitably terminated at the cylinder opening, or passed across the cylinder head opening.
The referenced application Ser. No. 214,720, filed Dec. 9, 1980, LINDER et al, describes a sensor arrangement in which a window is located at a portion of the inner wall of the combustion chamber, the window being formed at the side facing the combustion chamber with a contoured, preferably outwardly bulged or bowed shape, the contour forming edges, points, or the like, so that the contoured surface will be substantially larger, and interrupted, than a projected surface of the window itself. The combustion gas flows past the combustion chamber so that, upon swirling of the combustion gases, deposits which may accumulate on the window are cleaned off. A coating, for example of silver, can be applied to the surface of the window exposed to the combustion chamber to additionally assist in cleaning thereof.
The referenced application Ser. No. 214,513, filed Dec. 9, 1980, MAURER et al, describes a sensor arrangement in which a receiver is placed behind a chamber which extends from the combustion chamber and is open thereto. The receiver is formed as a unitary plug, which can be screwed into an opening formed in the cylinder head, for example, the chamber being closed off by a light transmissive window. An optical receiver can be located either directly behind the light transmissive window or a light guide can be coupled to the window for remote positioning of an optical transducer. A filter can be interposed between the window and the light guide, the filter being arranged to be responsive to specific spectral lines occurring during combustion, for example responsive to CO, HC, or OH components, with separate evaluation transducers being connected to the respective filters which, in turn, are connected to a comparator or divisor circuit, so that a quotient of signals representative of the respective spectral components is obtained, thus eliminating amplitude variations from the resulting output.